A variety of marine structures are employed in drilling and production of offshore oil wells. Offshore platforms are held in position at a fixed point above the marine bottom by guying the structures so as to be able to withstand natural forces, surface vessels and floating objects. So-called guyed towers are elongated, non-buoyant structures which require stabilizing in order to remain vertical. A typical guyed tower is described in U.S. Pat. No. 3,903,705, wherein a number of guy lines are arranged radially around the periphery of the marine structure near the water surface. Anchor means, such as clump weights, may be used to attach one end of each guy line to the marine floor to provide tension in the guy lines.
Positive buoyancy structures may also require similar tensioned cables to prevent sway or excessive tilting. Various offshore platforms of this type are known, for instance as described in U.S. Pat. No. 4,170,186, which discloses a technique for anchoring a buoyant structure by tension leg means. Often the guy lines are continuous cables which are attached to the platform above water, with a portion at or near the surface being exposed. In some constructions, the cable is guided by a below-surface sheave or fairlead attached to the structure for guiding the guy lines and permitting vertical movement of the lines. The upper end of the guy line is attached to the platform above water, either by fixed means, by winches or other cable adjustment means. The configuration of many offshore platforms provides an area of vulnerability to damage or loss of strength in the guy line between the above water platform and the area near the water surface. Damage or loss of strength could occur from fire on the platform or from vessel impact. If a sufficient number of lines were rendered ineffective, the tower stability could be severely impaired or the entire structure could be lost.
It is an object of the present invention to provide a fail-safe mechanism for retaining a large degree of structural stability sufficient to prevent overturning or loss of the marine structure.